BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a multi-layered printed-coil substrate for use as
planar magnetic components, wherein the multi-layered printed-coil substrate includes
a single or a plurality of substrates which has patterned coils.
Description of the Background Art
[0002] Wound magnetic components are known in the art and in common use as transformers
and choke coils used in the switched mode power supply circuits and the like. The
known wound magnetic component is composed of a bobbin having lead terminals, the
bobbin being wound with an enamel wire or the like. This type of magnetic components
are advantageous in that the number of turns and turn ratios can be readily changed
so as to obtain an optimum transformer ratio, thereby facilitating the designing and
developing of circuits, especially the manufacturing of transformers having an optimum
transformer ratio.
[0003] In general, the industry is in a strong need for reduction in the size and weight
of electronic devices, and such demands are reflected in the minimizing of circuit
components. As one of the proposals for meeting such demands, planar magnetic components
have been developed instead of the conventional wound magnetic components. Examples
of planar magnetic components are disclosed in Japanese Patent Publication Nos. 39-6921,
41-10524, and Laid-Open Publication No. 48-51250. The planar magnetic component is
not fabricated by winding a wire into a coil but, for example, a flat insulating substrate
is used on which a conductive pattern is formed with a thin film in a letter-U form
or a spiral form. In this way a printed-coil substrate is obtained. A single substrate
or several substrates are layered into a unit which is then sandwiched between magnetic
cores. However, the number of turns is limited because of the restricted space on
the substrate. To overcome this limitation, it is required that several printed-coil
substrates are layered into a single unit.
[0004] Planar magnetic components are advantageous in that the size and height can be minimized,
and the leakage inductance is minimized because of an increased area for interlinkage
of the magnetic flux thereby to strengthen coupling between the primary and secondary
windings, and the minimized copper loss due to skin effect. In addition, the coil
is formed by etching which is more stable than the wire winding, thereby enhancing
productivity and maintaining quality control. Among these advantages the high coupling
between the primary and secondary windings and the restraint of copper loss will be
more appreciated when the components are used under a high frequency current. In the
field of switched mode power supply circuit where the use of high frequency current
is becoming more and more popular, planar magnetic components call the industry's
attention.
[0005] FIG. 1 shows examples disclosed in Japanese Patent Laid-Open Publications Nos. 61-74311
and 61-75510, for example. A wiring substrate 41 is composed of layered insulating
sheets each having coil patterns 45 formed thereon. The wiring substrate 41 as a whole
constitutes a multi-layered printed-coil substrate used for a transformer. The wiring
substrate 41 is provided with through-holes 42 through which terminals 43 in the form
of pins (hereinafter "pin terminals" ) are inserted and soldered thereto, thereby
ensuring that the coil patterns 45 on one substrate and another are electrically connected.
One end of each pin terminal 43 is extended as shown in FIG. 1C and used as a connector
to an external conductor (not shown). The wiring substrate 41 is sandwiched between
a pair of split cores 44 and 46. In this way a magnetic circuit is completed in the
transformer.
[0006] FIG. 2 shows another example of planar magnetic component which is disclosed in Japanese
Utility Model Laid-Open Publication No. 4-103612. A coil pattern 52 is formed in a
spiral form on a wiring substrate 51. The wiring substrate 51 is provided with three
apertures 53, 54 and 55. A pair of ferrite cores 56 and 57 are prepared; the core
56 is provided with three projections adapted for insertion through the apertures
53, 54 and 55 of the wiring substrate 51. The core 57 is provided with recesses for
receiving the projections of the core 56. In this way a magnetic circuit for transformers
is formed.
[0007] FIGS. 3 and 4 show further examples which are disclosed in Japanese Utility Model
Laid-Open Publication No. 4-105512, Patent Laid-Open Publications Nos. 5-291062 and
6-163266. The illustrated thin-type transformer includes a multi-layered printed-coil
substrate 62 placed on a base 63 which is provided with pin terminals 65 each of which
includes a vertically extending portion 65a and a horizontally extending portion 65b.
The vertically extending portions 65a are inserted through through-holes 66 in the
multi-layered printed-coil substrate 62 and soldered thereto so as to effect electrical
connection. The multi-layered printed-coil substrate 62 is sandwiched between an I-shaped
core 64 and an E-shaped core 61, thereby forming a complete planar magnetic component.
The finished component is connected to an external conductor through the horizontally
projecting portions 65b.
[0008] The known planar magnetic components have advantages pointed out above, but on the
other hand, they inherently have the difficulty of changing the number of turns and
ratios of winding, and when these changes are wanted, a fresh printed-coil substrate
must be fabricated after a new coil pattern is designed. This involves a time- and
money-consuming work. Eventually, the components must be used where the number of
turns and ratio of winding are fixed. The advantages inherent in planar magnetic component
are not fully utilized.
[0009] The example shown in FIG. 1 has difficulty in enabling the pin terminals 43 to align
with the through-holes 42 and vertically position therein. This aligning work is time-consuming,
which is reflected in the production cost.
[0010] As far as the aligning is concerned, the examples of FIGS. 3 and 4 are more advantageous
than the example of FIG. 1 because of using the base 63 having pin terminals 65 uprightly
fixed in alignment with the through-holes 66. The use of the base 63 can reduce the
number of producing steps. On the other hand, the complicated base 63 is costly, so
that the whole production cost cannot be reduced. For the purpose of mass-production,
one way is to standardize the base 63 in the shape (the size, the pin terminal pitches,
the number of pin terminals) but this is contradictory to users' demand. Users want
to have a variety of bases even in a small quantity in accordance with required magnetic
characteristics. If the bases are standardized in one or two fixed models, the range
of applications will be restricted. The examples of FIGS. 3 and 4 lack the freedom
of designing the configuration of bases, and there is no choice but to use expensive
bases 63.
[0011] In the example shown in FIG. 2 the coil pattern and the external conductor are constituted
on the same substrate, thereby requiring no terminal base or pin terminal. This example
is advantageous in that processing steps can be saved but a disadvantage is the lack
of freedom of design because of the requirement that the number of coil patterns and
the thickness of copper foils must be the same as those of the external conductor.
SUMMARY OF THE INVENTION
[0012] The present invention is directed to solve the problems discussed above, and a principal
object of the present invention is to provide a multi-layered printed-coil substrate,
a printed-coil substrate used in producing the multi-layered printed-coil substrate
and a process of producing the multi-layered printed-coil substrate, thereby providing
planar magnetic components which secure the freedom of design so as to meet various
needs without increasing the production cost.
[0013] One object of the present invention is to provide a process of producing a multi-layered
printed-coil substrate by layering a predetermined number of printed-coil substrates,
the process comprising the steps of preparing several types of printed-coil substrates
having individually different coil patterns; selecting desired printed-coil substrates
from the prepared substrates, and layering the selected printed-coil substrates to
form a multi-layered printed-coil substrate.
[0014] Preferably, the types of prepared printed-coil substrates are different from each
other in at least one of the factors including the number of turns, the coil shape,
the coil width and the coil thickness.
[0015] Preferably, each of the prepared printed-coil substrates is provided with through-holes
for electrical connection between one and the next of the selected printed-coil substrates.
In addition, each of the prepared printed-coil substrates may be provided with connectors
for electrical connection between the selected printed-coil substrates and an external
conductor.
[0016] Another object of the present invention is to provide a process of producing a multi-layered
printed-coil substrate by layering printed-coil substrates, the process comprising
the steps of preparing several types of printed-coil substrates having individually
different coil patterns; selecting desired first printed-coil substrates from the
prepared substrates; layering the selected first printed-coil substrates to obtain
a prototype multi-layered printed-coil substrate; forming second printed-coil substrates
having characteristics demonstrated through the prototype multi-layered printed-coil
substrate; and layering the second printed-coil substrates to obtain a commercial
multi-layered printed-coil substrate having desired characteristics to meet various
needs.
[0017] Preferably, the multi-layered printed-coil substrate includes a connector for electrical
connection to an external conductor, wherein each of the printed-coil substrates is
provided with through-holes, and is supported by an insulating base having pin terminals
erected thereon for insertion into the through-holes in the substrates, thereby effecting
electrical connection between the pin terminals and the through-holes.
[0018] A still further object of the present invention is to provide a group of printed-coil
substrates for use in producing a multi-layered printed-coil substrate, the substrates
in the group being different from each other in at least one of the factors including
the number of turns, the coil shapes, the coil width and the coil thickness.
[0019] Preferably, the group of printed-coil substrates selected for producing a multi-layered
printed-coil substrate may include ones whose numbers of turns are expressed in an
integer and/or in a decimal fraction.
[0020] The above and further objects and features of the invention will more fully be apparent
from the following detailed description with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021]
FIGS. 1A to 1C are respectively a front view, a plane view and a side view showing
a known planar magnetic component;
FIG. 2 is an exploded perspective view showing another known planar magnetic component;
FIG. 3 is a perspective view showing a further known planar magnetic component;
FIG. 4 is an exploded perspective view showing the known planar magnetic component
shown in FIG. 3;
FIGS. 5A and 5B are exploded perspective views exemplifying the steps of producing
a multi-layered printed-coil substrate according to the present invention;
FIG. 6 is a circuit diagram of a switched mode power supply;
FIG. 7 is an exploded perspective view showing an example embodying the present invention;
FIG. 8 is an exploded perspective view showing another example embodying the present
invention;
FIG. 9 is a plane view showing an example of printed-coil substrate as a constituent
of the multi-layered printed-coil substrate;
FIG. 10 is a plane view showing several printed-coil substrates formed in a single
sheet;
FIG. 11 is a plane view showing another aspect of the printed-coil substrates shown
in FIG. 10;
FIG. 12 is a plane view showing a further aspect of the printed-coil substrates shown
in FIG. 10;
FIG. 13 is a plane view showing another example of printed-coil substrate as a constituent
of the multi-layered printed-coil substrate;
FIG. 14 is an exploded perspective view showing a prototype planar transformer;
FIGS. 15A and 15B are side views showing the prototype planar transformer shown in
FIG. 14;
FIG. 16 is an exploded perspective view showing a commercial planar transformer;
FIG. 17 is a side view showing the commercial planar transformer shown in FIG. 16;
FIGS. 18A and 18B are plan views showing a printed-coil substrate having decimal number
of turns;
FIG. 19 is a plan view showing electrical connection in a known manner;
FIG. 20 is a plan view showing electrical connection according to the present invention;
FIG. 21 is an exploded perspective view showing an example according to the present
invention;
FIGS. 22A, 22B and 22C are respectively a plane view, a front view and a side view
showing the example shown in FIG. 14;
FIG. 23 is an exploded perspective view showing a planar transformer using a printed-coil
component according to the present invention;
FIGS. 24A, 24B and 24C are respectively a plan view, a front view and a side view
showing the planar transformer using the printed-coil component shown in FIG. 23;
FIGS. 25A and 25B are schematic side views showing two examples of the manner in which
the transformer is mounted on a circuit board;
FIG. 26 is an exploded perspective view showing another example of a printed-coil
component according to the present invention; and
FIGS. 27A and 27B are a partial plane view showing a printed-coil substrate having
slits, and a partial side view showing an assembly of the slitted substrate, respectively.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] The present invention will be described by way of examples by reference to the drawings.
In FIGS. 5A and 5B, a plurality of printed-coil substrates are prepared wherein each
substrate has a conductive coil having different turns printed in a predetermined
pattern on one face or on both faces. From the prepared substrates desired substrates
(in the illustrated embodiment, five substrates 1a to 1e) are selected, and placed
in layers as shown in FIG. 5A. The pile is clamped by cores 11 and 12 on top and bottom.
Each core includes projections in the middle and on each edges, having an E-shape
in cross-section. Each printed-coil substrate 1a to le has a rectangular aperture
2 which allows the middle projection of each core 11 and 12.
[0023] The substrates 1a to 1e are integrated into a single body 3, hereinafter referred
to as "multi-layered printed-coil substrate 3" , and the cores 11 and 12 are fixed
to the multi-layered printed-coil substrate 3 by inserting the middle projections
thereof in its apertures 2 until both projections come into abutment with each other.
In this way a planar magnetic component is finished.
[0024] Now, an example of applications will be described by reference to FIG. 6. The exemplary
circuit is a forward type switched mode power supply circuit which uses a multi-layered
printed-coil substrate of the present invention. The multi-layered printed-coil substrate
of the invention is used as a transformer 13 and a choke 14. The exemplary switched
mode power supply is responsive to an input voltage of 36 to 72V. An output voltage
is divided by a resistor, and amplified by comparison with a reference voltage of
a variable Zener diode 19. Then it is inputted to a feed-back voltage terminal for
a PWM (Pulse Width Modulation) IC 15 through a photo-diode 17 and a photo-transistor
18. In general, in a forward type switched mode power supply circuit the output voltage
and the duty ratio (time ratio of on-time period to pulse period) of the MOSFET switch
16 are mutually proportional. The PWM IC 15 controls the duty ratios of pulses to
the MOSFET in accordance with the voltages at the feed-back voltage terminal, thereby
maintaining the output voltage at a predetermined value. At the switched mode power
supply circuit as the output voltage rises (falls), the photo-diode 17 increases (decreases)
brightness, thereby causing the voltage at the feed-back voltage terminal connected
to the emitter of the photo-transistor 18 to rise (fall). As a result, the duty ratio
of the MOSFET driving pulses of the PWM IC 15 lowers (rises), thereby regulating the
output voltage to a determined value.
[0025] In order to produce magnetic components used for the transformer 13 and the choke
14, six types of printed-coil substrates each having different number of turns were
prepared. Each type of substrate had conductive patterned coils and having the same
on each face. The number of turns on each face of the six types of substrates are
summarized as follows:
L1: 2 turns |
L2: 3 turns |
L3: 4 turns |
L4: 5 turns |
L5: 6 turns |
L6: 7 turns |
[0026] Since it is required to limit the height of the planar magnetic component including
the cores to 5mm or less, the maximum number of printed-coil substrates is six. Table
1 shows examples of selected substrates for the transformer 13 and the choke 14. The
number of substrates are five as shown in FIG. 5A. The 1st to 5th substrates in Table
1 correspond to the substrates 1a to 1e in FIG. 5A.
TABLE 1
Substrates |
Transformer (13) |
Choke (14) |
|
primary/secondary |
substrate |
primary/secondary |
|
1st (1a) |
primary |
L 5 |
secondary |
L 1 |
2nd (1b) |
secondary |
L 1 |
primary |
L 6 |
3rd (1c) |
primary |
L 5 |
secondary |
L 1 |
4th (1d) |
secondary |
L 2 |
primary |
L 6 |
5th (1e) |
primary |
L 5 |
secondary |
L 1 |
[0027] In the illustrated example the primary coil and secondary coil are alternately layered
so as to strengthen the coupling between the primary and secondary windings.
[0028] The planar magnetic components obtained by integrating the five substrates 1a to
1e shown in Table 1 and sandwiching them between the cores 11 and 12 were used in
the transformer 13 and the choke 14 with the switching circuit shown in FIG. 6. It
was found that the efficiency of the switched mode power supply remarkably increased
by as high as 85%. This is greatly due to the high coupling between the primary and
secondary windings which improves the performance of a planar magnetic component.
[0029] In general, a 10-layered printed-coil substrate costs ¥500,000.- to ¥600,000.- and
takes at least a month to make it. In addition, it is necessary to change the number
of turns several times for use in transformers and chokes. Under the conventional
practice several types of multi-layered printed-coil substrates having particular
number of turns and turn ratios are prepared and stored, and when necessary, an appropriate
prototype is selected in accordance with the desired specification. This practice
limits the range of applicability of planar magnetic components to limited industrial
fields, and therefore, the advantages of planar magnetic components cannot be fully
utilized. Advantageously, according to the present invention, a variety of printed-coil
substrates having different number of turns can be selected as desired from a stock
according to use. If they are intended for use in equipment subjected to changes in
the input and output voltages at the switched mode power supply, the printed-coil
substrates of the present invention can be readily adjusted to the needs, thereby
securing the freedom of design. A further advantage is that the performance test can
be done in a relatively short time and the production cost is saved. In the illustrated
example, the same number of turns is patterned on each face. It is possible to differ
the number of turns between both faces, and to form a coil pattern one face alone.
Furthermore, it is possible to combine two types of printed-coil substrates having
coil patterns on one face and on both faces.
[0030] Various modifications are possible, for example, by changing the configuration of
coiling, the width and/or thickness of the printed-coil. Substrates having modified
coils are prepared and stored for selection at the assembly process. This secures
the freedom to manufacture multi-layered printed-coil substrates to various requirements.
[0031] Next, referring to FIG. 7, the manner of electrical connection of the printed-coil
substrates will be described:
[0032] In FIG. 7, the printed-coil substrates la to le each having predetermined patterns
of coils 4 on both faces and through-holes 5 for electrical connection between both
faces. Each substrate la to le has a terminal 6 on an extruded portion in the short
side and a downward-projecting clip-lead 7 detachably fixed to the terminal 6. The
clip-leads 7 are used not only for electrical connection between the printed-coil
substrates but also for electrical connection to an external conductor through electrical
connection to the patterns formed in a mounting substrate.
[0033] Referring to FIG. 8, wherein like reference numerals designate like elements and
components to those in FIG. 7, a modified version will be described:
[0034] This example is different from the example shown in FIG. 7 in that the short side
has an extruded part in which another through-holes 8 supporting pin-terminals 9 are
formed. The pin-terminals 9 function in the same manner as the clip-leads 7.
[0035] In general, unlike wound magnetic components planar magnetic components become more
costly in proportion to the number of printed-coil substrates to be used, especially
in the initial costs incurred in designing and preparing patterning films for etching.
If a reduction in the production cost is wanted on condition that the tested performances
of multi-layered printed-coil substrates are maintained, the following method is possible
according to the present invention:
[0036] First, reference will be made to the types of printed-coil substrates. FIG. 9 shows
three types of substrates A, B and A' each having patterned coils on both faces and
having four terminals at each side of the face. The back face is opposite to the front
face. The reference numerals 4 and 5 denote a coil having a predetermined pattern,
and through-holes 5 which connect one of the faces to another, respectively. Each
substrate is provided with four pin pads 10 along the opposite sides, each of the
pin pads 10 including a through-hole 8, through which a pin terminal is inserted for
electrical connection between the substrates.
[0037] These substrates can be classified according to which of the through-holes 8 corresponds
to a starting end and a ending end of winding. More particularly, in the top face
of the substrate A the 1st through-hole 8 in the bottom row corresponds to the starting
end of the coil winding, and the 2nd through-hole 8 in the same row corresponds to
the ending end of the coil 4. Likewise, in the substrate B the 2nd through-hole from
the left in the bottom row corresponds to the starting end of winding, and the 3rd
through-hole 8 in the same row corresponds to the ending end of winding. In the substrate
A' the 3rd through-hole in the bottom row corresponds to the starting end of winding
and the 4th through-hole in the same row corresponds to the ending end of winding.
The substrate A' can be obtained by turning the substrate A upside down, and therefore
they are substantially the same. When four terminals are provided at each side of
the face, the printed-coil substrate can have two types, that is, the substrates A
and B, and printed-coil substrates having several turns are prepared for each type.
An example is shown in Table 2 in which the substrates have various number of turns
ranging from 1 to 6:
TABLE 2
Substrates |
Type |
Number of Turns |
A1 |
A |
1 |
A2 |
A |
2 |
A3 |
A |
3 |
A4 |
A |
4 |
A5 |
A |
5 |
A6 |
A |
6 |
B1 |
B |
1 |
B2 |
B |
2 |
B3 |
B |
3 |
B4 |
B |
4 |
B5 |
B |
5 |
B6 |
B |
6 |
[0038] The printed-coil substrates 1 are formed in one-piece as shown in FIG. 10, and they
are individually cut off along the V cut lines; in the illustrated example includes
nine printed-coil substrates 1 which are the same in every respect such as A1 in Table
2. The V cut lines are designed to facilitate the separation of individual substrates.
The twelve substrates A1 to B6 shown in Table 2 have the shaded portions shown in
FIGS. 11 and 12 cut off, and have a shape shown in FIG. 13. The back face of each
substrate is opposite to the front face. Like reference numerals designate like reference
numerals to those in FIG. 9. The reason for removing the shaded portions is that the
pin terminals may be readily and effectively soldered to the pin pad 10. However,
if no problem is likely to arise, it is unnecessary to remove the shaded portions.
[0039] Before the commercial multi-layered printed-coil substrates are assembled on a regular
manufacturing basis, prototype multi-layered printed-coil substrates are obtained
as follows:
[0040] After desired substrates 1 are selected and layered to obtain a prototype multi-layered
printed-coil substrate which is then provided with through-holes 8 and pin terminals
9 inserted through the through-holes 8 and sandwiched between the cores 11 and 12.
In this way a planar transformer is finished as shown in FIG. 14 as an exploded perspective
view. FIGS. 15A and 15B are side views showing the planar transformer. In the illustrated
example, five printed-coil substrates 1a to 1e are selected and layered into a single
unit. The pin terminals 9 inserted through the through-holes 8 and the pin pads 10
are soldered to each other with fillet solder 20.
[0041] After several multi-layered printed-coil substrates are obtained, each of which is
tested and assessed. The manufacturers can decide the types and the order of layering
by referring to the test results. Then commercial multi-layered printed-coil substrate
is assembled in the following manner:
[0042] The regular manufacturing process is started by producing several printed-coil substrates
1. First, a film used in fabricating an initial model for design use is again used,
and several printed-coil substrates are formed together in one sheet as shown in FIG.
10. The used film can be used, thereby saving the production cost. The printed-coil
substrates 1 formed in one sheet and are individually separated in the aforementioned
manner, and then are layered into a multi-layered printed-coil substrate 3. An insulating
sheet containing adhesive is inserted between the adjacent substrates so that they
are bonded in an insulating state. The pin terminals 9 are inserted through the through-holes
8 and the multi-layered printed-coil substrate 3 is sandwiched between the cores 11
and 12. In this way a planar transformer is finished which is shown in FIGS. 16 and
17.
[0043] The printed-coil substrates 1 are formed in one sheet and individually separated,
but it is possible to use them as a prototype model without being cut away from the
sheet.
[0044] In the illustrated example pin terminals 9 are used as a connector one substrate
to another. The clip-leads 7 shown in FIG. 7, which are cheaper than the pin terminals,
can be also used as a connector.
[0045] In the example the number of turns is an integer but it can be 0.75, 0.5 or any other
decimal figures. FIG. 18A shows a printed-coil 4 having coil turns of 0.75, and FIG.
18B shows a printed-coil 4 having coil turns of 0.5. In electrically connecting two
pin pads 10 in opposite to the core 11, the printed-coil 4 having coil turns of 0.75
is advantageous in that as shown in FIG. 20 the two pin pads 10 can be electrically
connected by increasing the number of turns, in contrast to the prior art example
where electrical connection between the two pin pads 10 are effected by use of an
external conductor 101 as shown in FIG. 19.
[0046] When the number of turns is an integer and four terminals are provided at each side
of the face, there can be two types of substrates depending upon the starting end
and the ending end of winding as described above. Table 3 shows the relationship between
the number of types of printed-coil substrates depending upon the starting end and
the ending end of winding wherein the number of turns is an integer. In order to withstand
heavy current, it is preferred that the through-holes 8 are branched near the starting
end or the ending end of winding so as to provide a plurality of pin terminals in
parallel, which increases in the number of pin terminals.
TABLE 3
Number of Terminals |
Types of the Substrates |
2 |
1 |
3 |
1 |
4 |
2 |
5 |
2 |
6 |
3 |
7 |
4 |
[0047] Referring to FIG. 21, printed-coil components used in electrically connecting the
printed-coil substrates and an external conductor will be described:
[0048] The printed-coil substrate 21 is a rectangular thin body in which coils patterned
in a conductor are layered in multi-layers. The substrate 21 is stiff sufficiently
to stand by itself without any support. The substrate 21 includes a rectangular aperture
21a in the center, and is provided with through-holes 23 (in the illustrated example,
6 holes) at equal intervals, which are open in pin pads 22, along the opposite short
sides. The substrate 21 is placed on a pair of bases 25 made of an insulating material
on which pin terminals 24 of conductor (in the illustrated example, 6 pieces) are
erected at equal intervals to those among the through-holes 23. Each base 25 is additionally
provided with projections of conductor 26 on its side, hereinafter the projection
26 will be referred to as "side projection" . Each pin terminal 24 is longer than
the length of the through-hole 23, preferably about two times long.
[0049] The printed-coil component will be assembled in the following manner:
[0050] Referring to FIGS. 22A, 22B and 22C, which are respectively a plane view, a front
view and a side view showing a finished assembly, the substrate 21 and the bases 25
are positioned by aid of a jig such that the through-holes 23 of the substrate 21
and the pin terminals 24 on the bases are aligned. The pin terminals 24 are inserted
through the through-holes 23 until the substrate 21 comes into abutment with the bases
25, and are soldered thereto so as to secure electrical connection therebetween, wherein
the reference numeral 27 denotes a solder fillet. As is evident from FIGS. 22B and
22C, half of the pin terminals 24 project above the top surface of the substrate 21.
[0051] The assembly obtained in this way is sandwiched between the E-shaped core and the
I-shaped cores. In this way a transformer for use in a switched mode power supply
circuit and a choke coil are obtained. FIG. 23 is an exploded perspective view showing
a finished transformer, and FIGS. 24A, 24B and 24C are respectively a plane view,
a front view and a side view showing the transformer in an assembled state. In FIGS.
23 and 24 like reference numerals designate like elements and components to those
in FIGS. 21 and 22, and a description of them will be omitted for simplicity.
[0052] In FIGS. 23 and 24 the printed-coil component is sandwiched between the ferrite cores
28 and 29; more specifically, the E-shaped core 28 having projections in the middle
and each edge, and the core 29 is a rectangular flat I-shaped body. The middle projection
of the core 28 is inserted through the aperture 21a until the three projections thereof
come into abutment with the core 29. In this way the printed-coil component and the
cores 28, 29 are integrated into a single body, which provides a transformer.
[0053] The transformer and a mounting base are electrically connected in the following manner:
[0054] Referring to FIGS. 25A and 25B, wherein like reference numerals designate like elements
and components to those in FIGS. 23 and 24:
[0055] Each side projection 26 electrically connected to the pin terminals 24 is soldered
to the mounting base 30 with solder fillets 31, thereby securing electrical connection
between the printed-coil component and the mounting base 30. The example shown in
FIG. 25A has the bases 25 having a shortened height so that the ferrite core 29 is
placed in contact with the mounting base 30. This arrangement is advantageous in that
heat generated from the ferrite core is allowed to dissipate through the mounting
base 30. In FIG. 25B the height of the bases 25 are adjusted so that the bottom of
the ferrite core 29 is maintained slightly above the mounting base 30, thereby ensuring
that the ferrite core 29 and the mounting base 30 are insulated from each other.
[0056] According to the present invention, the printed-coil substrate 21 and the cores can
be easily assembled by aligning the pin terminals 24 with the through-holes 23 by
use of a simple jig in contrast to the prior art in which pin terminals 43 (FIG. 1)
are upright pressed into the through-holes 42. After the intervals of the pin terminals
24 on each base 25 are fixed, it is no longer necessary to care about the number of
them and the distance of opposite pin terminals 24 on the bases 25. Thus the flexibility
of design is ensured unlike the prior art example shown in FIGS. 3 and 4 using the
base 63 where not only the intervals of the pin terminals 65 but also the number of
the pin terminals 65 and the distance of opposite pin terminals 65 are fixed. The
flexibility of design reduces costs incurred not only in procuring raw material but
also in manufacturing.
[0057] Referring to FIG. 26, a modified version will be described:
[0058] The illustrated example includes three printed-coil substrates 21 and four insulating
sheets 32 alternately layered, wherein the patterned coils are formed on both faces
of each substrate. Each insulating sheet 32 includes a rectangular aperture 32a in
the center corresponding to the aperture 21a, and additionally, through-holes 33 along
each short side, corresponding to the through-holes 23 of the substrate 21. The printed-coil
substrates 21 are electrically connected to each other in the same manner as described
above, that is, by using the bases 25, inserting the erected pin terminals 24 thereon
through the through-holes 23 and 33, and soldering the pin terminals 24 to and around
the through-holes 23 and 33. In general, the production cost rises in proportion to
the number of layers of printed-coil patterns formed on the substrates, wherein the
rise is exponential functional. When a number of printed-coil patterns are to be used,
it is preferred to distribute the patterns into several substrates, and layer them
with a single or several insulating sheets interlocated between the adjacent substrates
as shown in FIG. 26.
[0059] Referring to FIG. 27, a modified version of the printed-coil component according
to the present invention will be described, wherein like reference numerals designate
like elements and components to those in FIG. 21:
[0060] The printed-coil substrate 21 is provided with slits 34 leading to each of the through-holes
23 and being open therein. The slits 34 are useful for visually inspecting the state
of bond between the pin terminals 24 and the through-holes 23, thereby contributing
to quality control. The pin terminals 24 can be exactly positioned by reliance upon
the through-holes 23. To achieve this convenience, the width of each slit 34 should
be narrower than the diameter of the pin terminal 24.
[0061] In the examples of printed-coil components described above, the shape and location
of the pin terminals 24, the shape of the through-holes 23 in the printed-coil substrate
21, the number of pattern layers, the number of printed-coil substrates to be layered,
and the shape of ferrite cores are not limited to the illustrated examples but they
can be appropriately selected or determined.
[0062] As this invention may be embodied in several forms without departing from the spirit
of essential characteristics thereof, the examples described herein are illustrative
and not restrictive, since the scope of the invention is defined by the appended claims
rather than by the description preceding them, and all change that fall within metes
and bounds of the claims, or equivalent of such metes and bounds thereof are therefore
intended to be embraced by the claims.
1. A process of producing a multi-layered printed-coil substrate consisting of printed-coil
substrates each having patterned coils in a single or several layers, the process
comprising the steps of:
preparing several types of printed-coil substrates having individually different
coil patterns;
selecting desired printed-coil substrates from the prepared printed-coil substrates;
and
layering the selected printed-coil substrates to form a multi-layered printed-coil
substrate.
2. The process according to claim 1, wherein the prepared printed-coil substrates have
printed-coils on one face or on both faces thereof.
3. The process according to claim 1, wherein the types of prepared printed-coil substrates
are different from each other in at least one of the factors including the number
of turns, the coil shape, the coil width and the coil thickness.
4. The process according to claim 1, wherein each of the prepared printed-coil substrates
is provided with through-holes for electrical connection between the printed-coils
on both faces thereof.
5. The process according to claim 1, wherein each of the prepared printed-coil substrates
is provided with connectors for electrical connection between one and another of the
layered printed-coil substrates and/or between the substrates and an external conductor.
6. The process according to claim 5, wherein the connector is a clip-lead, and each of
the printed-coil substrates is provided with terminals connected to the clip-lead.
7. The process according to claim 5, wherein the connector is a pin terminal, and each
of the printed-coil substrates is provided with through-holes for insertion of the
pin terminal.
8. A process of producing a multi-layered printed-coil substrate consisting of printed-coil
substrates each having patterned coils in a single or several layers, the process
comprising the steps of:
preparing several types of printed-coil substrates having individually different
coil patterns;
selecting desired printed-coil substrates from the prepared printed-coil substrates;
layering the selected printed-coil substrates to obtain a prototype multi-layered
printed-coil substrate;
forming printed-coil substrates having the same characteristics as those of the
selected printed-coil substrates used in the prototype multi-layered printed-coil
substrate; and
layering the last-mentioned printed-coil substrates to obtain a multi-layered printed-coil
substrate having the same characteristics with those of the prototype multi-layered
printed-coil substrate.
9. The process according to claim 8, wherein the last-mentioned printed-coil substrates
are formed by the same pattern film used in forming the prepared printed-coil substrates.
10. A group of printed-coil substrates for use in producing a multi-layered printed-coil
substrate, the substrates in the group being different from each other in at least
one of the factors including the number of turns, the coil shapes, the coil width
and the coil thickness.
11. The group of printed-coil substrates according to claim 10, wherein the substrates
have printed-coils on one face or on both faces thereof.
12. The group of printed-coil substrates according to claim 10, wherein each substrate
is provided with through-holes so as to effect electrical connection between the printed-coils
on both faces thereof.
13. The group of printed-coil substrates according to claim 10, wherein each substrate
is provided with connectors for electrical connection between one and another of the
layered printed-coil substrates and/or between the substrates and an external conductor.
14. The group of printed-coil substrates according to claim 13, wherein the connector
is a clip-lead, and each of the printed-coil substrates is provided with terminals
connected to the clip-leads.
15. The group of printed-coil substrates according to claim 13, wherein the connector
is a pin terminal and each of the printed-coil substrates is provided with through-holes
for insertion of the pin terminal.
16. The group of printed-coil substrates according to claim 10, wherein the number of
turns of each of the printed-coil substrates selected for lamination is expressed
in an integer.
17. The group of printed-coil substrates according to claim 10, wherein the number of
turns include a decimal fraction.
18. A printed-coil component including a multi-layered printed-coil substrate consisting
of printed-coil substrates each having patterned coils in a single or several layers
and a connector for electrical connection to an external conductor, wherein the printed-coil
substrate is provided with through-holes, and is supported by an insulating base having
pin terminals erected thereon for insertion into the through-holes of the substrates,
thereby effecting electrical connection between the pin terminals and the through-holes.
19. The printed-coil component according to claim 18, wherein the printed-coil substrate
is provided with slits leading from an edge thereof to the through-holes, the slits
having a narrower width than the diameter of the pin terminals.
20. The printed-coil component according to claim 18, wherein the printed-coil substrates
are layered with insulating sheets interlocated therebetween.
21. A printed-coil substrate having patterned coils in a single or several layers, comprising
a plurality of through-holes and slits leading from an edge thereof to the through-holes,
each slit having a narrower width than the diameter of the pin terminals to be inserted
through the through-holes.